Langley, Hu Scientists Lend Hand To Promising Study Of Ozone Layer

A team that included Hampton University and NASA Langley scientists recently announced that ozone depletion was decreasing in the highest levels of the atmosphere, probably because of the phasing out of chemicals used in refrigerants and aerosol sprays.

The ozone layer blocks ultraviolet radiation from the sun that can cause skin cancer and harm ecosystems.

Nearly 30 years ago, scientists found that chlorine released into the stratosphere from chlorofluorocarbons -- chemicals used as refrigerants and aerosol propellants -- was destroying the ozone layer. This led to an international ban on products with these chemicals.

The chlorofluorocarbons began being phased out in 1989, but the effects of the phaseout are just beginning to be measured now because the chemicals take years to decay, scientists said.

Scientists used data collected over several years from NASA satellites and international ground stations.

The stations included the Stratospheric Aerosol and Gas Experiment, or SAGE, and HALOE, the Halogen Occultation Experiment.

"As the satellites orbit Earth, they see a sunset and a sunrise once every 90-minute orbit," said Michael J. Newchurch, an atmospheric chemist at the University of Alabama at Huntsville.

"The instruments look at the sun as it sets or rises, as sunlight is filtered through the atmosphere."

Scientists can measure how much ozone and other gases are present by studying the data that come from these readings of filtered sunlight.

"The findings showed the decrease in ozone has slowed down," Russell said. "That's a change we could only see thanks to these robust instruments in space for so long. They measure fractions of a percentage change per year."

But full recovery is still decades away, Russell said. The findings show a slowing in the rate of loss but not a reversal. Scientists also cautioned that the effects had been found only in the uppermost stratosphere, the layer of the atmosphere between 21 and 28 miles above the ground.

But 80 percent of the ozone layer exists in the lower atmosphere, the layer of atmosphere between 12 and 21 miles up.

To fix ozone depletion in the lower atmosphere, Newchurch said, other solutions will be necessary, such as studying greenhouse gases that include carbon dioxide and methane.

Still, the findings are promising, he said. "This is the beginning of a recovery of the ozone layer," Newchurch said. "We had a monumental problem of global scale that we have started to solve."